... solar water heaters for 16 years.Products got CE, SRCC, Keymark, ISO9001, CGC&CCC certificates.Consists of two layers of glass tubes Outer tube ... and low heat loss Outer tube transmittance: 0.91 Air is evacuated from space between two glass tubes to form vacuum, so ... CE certified Payment Details:Payment Terms:T/T, L/C solar vacuum tube for solar water heater